The overarching goal of the proposed research is to directly test the validity of the oxidative stress hypothesis of aging by determining the effects of genetic manipulations of the antioxidative defenses in Drosophila melanogaster. The specific hypothesis to be tested in the present study is that experimental augmentation of the glutathione (GSH) - NADPH system would lower the level of oxidative stress thereby slowing the rate of the aging process, while a decrease in the efficiency of this system would elevate the level of oxidative stress and accelerate the aging process. GSH and NADPH provide the bulk of the reducing power in cells and act in concert to eliminate various reactive oxygen species (ROS). Enhancement of cellular ability to synthesize GSH and NADPH will be achieved by transgenic overexpression of y-glutamate-cysteine ligase subunits (GCL) and glucose-6-phosphate dehydrogenase (G6PH), respectively, in D. melanogaster. The four specific aims are: (I) Determine the effects of over and under expression of GCL in different regions of the body and at different periods of life cycle on the aging process. (II) Determine the effects of over and under expression of glucose-6-phosphate dehydrogenase (G6PD) in different regions of the body and at different periods of the life cycle on the aging process. (Ill) Determine the effects of co-overexpression of GCL and G6PD on the life span and patterns of physiological aging. (IV) Determine the effects of over and under expression of GCL and G6PD on the redox state of tissues indicated by GSH, GSSG, mixed protein disulfides, NADPH, NADP+, NADH and NAD+. The most compelling rationale for these studies is that our recent findings indicate that overexpression of GCL (catalytic subunit) and G6PD increases life span of relatively long-lived strains of flies by up to 50%. Results of the prospective studies would directly test the predictions of the oxidative stress hypothesis of aging and indicate whether augmentation of cellular reductive capacity can significantly extend the life span of flies.